I would suggest to give bonus for good alignment unit using event offer to upgrade unit strenght or speed or UI or leadership bonus in a particular friendly city in a certain timeframe
eg.
A turn event may offer
1) pay 50 gold for 1 unit of crusader to gain attack +5 in a friendly city within 3 turns timeframe
2) pay 100 gold for 1 unit of gryphon to gain ambush +16 in a friendly city within 3 turns timeframe
3) pay 200 gold for 1 unit of unicorn to gain UI +5 in a friendly city within 2 turns timeframe
4) pay 300 gold for 1 unit of pegasus to gain groupmove +4 in a friendly city within 2 turns timeframe
5) pay 400 gold for 1 unit of archon to gain anti ambush +8 in a friendly city within 2 turns timeframe
6) pay 500 gold for 1 unit of great archon to gain negate aura +6 and anti air +15 in a friendly city within 2 turns timeframe